In recent years, in order to enhance the heat efficiency, the demand for operating turbines in higher temperature has increased, whereby the turbine inlet temperature reaches from 1200 to 1700 degrees Celsius. Under such high temperature, metal components, which are the structural bodies of the turbine, need to be cooled so as not to exceed a limit temperature of a material of the metal components. In order to cool the turbine components, cooling air paths are formed inside of the components and the cooling is performed from inside of the components. At this moment, high pressure air formed by a compressor is usually used as the cooling air. Therefore, the amount of air used for the cooling air affects the performance of a gas turbine directly.
A turbine blade is the turbine component which especially needs cooling. As a cooling structure for the turbine blade, the Impingement cooling structure in which an insert component for flowing the cooling air is prepared as a different component from the turbine blade and is assembled inside of the turbine blade (For example, Non Patent Document 1) or the Serpentine flow path cooling structure in which turning flow paths are formed inside of the turbine blade and the cooling air is circulated (For example, Patent Document 1 or Non Patent Document 2) are disclosed.    Patent document 1: Japanese Unexamined Patent Application, First Publication No. H06-167201.    Non Patent Document 1: Shigemichi Yamawaki, “Verifying Heat Transfer Analysis of High Pressure Cooled Turbine Blades and Disk”, Heat transfer in gas turbine systems (Annals of the New York Academy of Science), (United States), the New York Academy of Science, 2001, Volume 934, pp. 505-512    Non Patent Document 2: Je-chin Han et al., “Gas Turbine heat transfer and cooling technology”, (United Kingdom), Taylor & Francis, 2000, pp. 20